It is not uncommon for various structural objects to be built which include two spaced apart walls which form a relatively narrow vertical elongated space which is straight or curved. At times it is desirable, and even necessary, to apply a coating to one or both of the walls. The coating can be in the nature of a paint or it can be an insulating material, particularly a polymeric insulating material, such as one which is foamed in place.
A specific structure having a relatively narrow vertical elongated space between spaced apart walls is a storage tank for liquids stored at temperatures significantly above or below ambient temperature. Such a tank generally has inner and outer shells which include spaced apart inner and outer vertical cylindrical circular walls made of metal plate. The spaced apart walls define an annular space in which insulation is placed to retard heat leak through the walls. Such tanks are disclosed in U.S. Pat. Nos. 3,147,878 and 3,352,443. As disclosed in those patents, the insulating material can be a granular material such as expanded perlite, used alone or with a resilient insulating blanket.
While the described insulating systems have been satisfactory, it is desirable to further improve the insulation system. One way to do this is to apply a foamed-in-place insulating layer of a polymeric material, such as polyurethane, to one or both of the walls defining the annular space between the two tank walls. The annular space is generally only about 3 to 5 feet wide but 30 to 100 feet or more high. Manual application of foamed-in-place insulation to one or both of the walls in such cramped limiting space is tedious, difficult and expensive. A need accordingly exists for apparatus and methods of coating one or more of the walls in such narrow elongated space which can be operated automatically and remotely so as to avoid most or all need for manual coating the walls.
U.S. Pat. No. 4,167,151 discloses a vertical track having two rails on which a carriage rides vertically. The carriage has a spray gun by which foamed-in-place insulation is applied to a vertical surface. However, the apparatus is not taught to be useful in a narrow vertical space nor does it have means to releasably secure it in place in such space against lateral or sideways movement.